Can you round a .NET TimeSpan object?

Question

Can you round a .NET TimeSpan object?

I have a Timespan value of: 00:00:00.6193789

Is there a simple way to keep it a TimeSp

Answer 1

Simplest one-liner if you are rounding to whole seconds:

public static TimeSpan RoundSeconds( TimeSpan span ) {
    return TimeSpan.FromSeconds( Math.Round( span.TotalSeconds ) );
}

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To round to up to 3 digits (e.g. tenths, hundredths of second, or milliseconds:

public static TimeSpan RoundSeconds( TimeSpan span, int nDigits ) {
    // TimeSpan.FromSeconds rounds to nearest millisecond, so nDigits should be 3 or less - won't get good answer beyond 3 digits.
    Debug.Assert( nDigits <= 3 );
    return TimeSpan.FromSeconds( Math.Round( span.TotalSeconds, nDigits ) );
}

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For more than 3 digits, its slightly more complex - but still a one-liner. This can also be used for 3 or less digits - it is a replacement for the version shown above:

public static TimeSpan RoundSeconds( TimeSpan span, int nDigits ) {
    return TimeSpan.FromTicks( (long)( Math.Round( span.TotalSeconds, nDigits ) * TimeSpan.TicksPerSecond) );
}

If you want a string (according to a comment, this technique only works up to 7 digits):

public static string RoundSecondsAsString( TimeSpan span, int nDigits ) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < nDigits; i++)
        sb.Append( "f" );
    return span.ToString( @"hh\:mm\:ss\." + sb );
}

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For time of day, as hours and minutes, rounded:

public static TimeSpan RoundMinutes(TimeSpan span)
    {
        return TimeSpan.FromMinutes(Math.Round(span.TotalMinutes));
    }

If you have a DateTime, and want to extract time of day rounded:

DateTime dt = DateTime.Now();
TimeSpan hhmm = RoundMinutes(dt.TimeOfDay);

To display rounded 24 hour time:

string hhmmStr = RoundMinutes(dt.TimeOfDay).ToString(@"hh\:mm");

To display time of day in current culture:

string hhmmStr = new DateTime().Add(RoundMinutes(dt.TimeOfDay)).ToShortTimeString();

---

Credits:

cc1960's answer shows use of FromSeconds, but he rounded to whole seconds. My answer generalizes to specified number of digits.

Ed's answer suggests using a format string, and includes a link to the formatting document.

Chris Marisic shows how to apply ToShortTimeString to a TimeSpan (by first converting to a DateTime).

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To round to multiple of some other unit, such as 1/30 second:

    // Rounds span to multiple of "unitInSeconds".
    // NOTE: This will be close to the requested multiple,
    // but is not exact when unit cannot be exactly represented by a double.
    // e.g. "unitInSeconds = 1/30" isn't EXACTLY 1/30,
    // so the returned value won't be exactly a multiple of 1/30.
    public static double RoundMultipleAsSeconds( TimeSpan span, double unitInSeconds )
    {
        return unitInSeconds * Math.Round( span.TotalSeconds / unitInSeconds );
    }

    public static TimeSpan RoundMultipleAsTimeSpan( TimeSpan span, double unitInSeconds )
    {
        return TimeSpan.FromTicks( (long)(RoundMultipleAsSeconds( span, unitInSeconds ) * TimeSpan.TicksPerSecond) );

        // IF USE THIS: TimeSpan.FromSeconds rounds the result to nearest millisecond.
        //return TimeSpan.FromSeconds( RoundMultipleAsSeconds( span, unitInSeconds ) );
    }

    // Rounds "span / n".
    // NOTE: This version might be a hair closer in some cases,
    // but probably not enough to matter, and can only represent units that are "1 / N" seconds.
    public static double RoundOneOverNAsSeconds( TimeSpan span, double n )
    {
        return Math.Round( span.TotalSeconds * n ) / n;
    }

    public static TimeSpan RoundOneOverNAsTimeSpan( TimeSpan span, double n )
    {
        return TimeSpan.FromTicks( (long)(RoundOneOverNAsSeconds( span, n ) * TimeSpan.TicksPerSecond) );

        // IF USE THIS: TimeSpan.FromSeconds rounds the result to nearest millisecond.
        //return TimeSpan.FromSeconds( RoundOneOverNAsSeconds( span, n ) );
    }

To use one of these to round to multiples of 1/30 second:

    private void Test()
    {
        long ticks = (long) (987.654321 * TimeSpan.TicksPerSecond);
        TimeSpan span = TimeSpan.FromTicks( ticks );
        TestRound( span, 30 );
        TestRound( TimeSpan.FromSeconds( 987 ), 30 );
    }

    private static void TestRound(TimeSpan span, int n)
    {
        var answer1 = RoundMultipleAsSeconds( span, 1.0 / n );
        var answer2 = RoundMultipleAsTimeSpan( span, 1.0 / n );
        var answer3 = RoundOneOverNAsSeconds( span, n );
        var answer4 = RoundOneOverNAsTimeSpan( span, n );
    }

Results viewed in debugger:

// for 987.654321 seconds:
    answer1 987.66666666666663  double
    answer2 {00:16:27.6666666}  System.TimeSpan
    answer3 987.66666666666663  double
    answer4 {00:16:27.6666666}  System.TimeSpan

// for 987 seconds:
    answer1 987 double
    answer2 {00:16:27}  System.TimeSpan
    answer3 987 double
    answer4 {00:16:27}  System.TimeSpan